A desirable ventilation system should be simple in structure, and ventilation equipment can be adjusted according to actual conditions for safety production. The quality of the ventilation equipment has a significant impact on the ventilation effect. The existing moving blade adjustable axial flow fan is usually driven by a hydraulic system to adjust the installation angles of blades. The hydraulic system generally includes a pump, a pipeline, a servo valve, a servo cylinder and the like, wherein considerable parts of components need to be specially made, so that the overall manufacturing process of the system is complex and the maintenance cost is high. Besides, when the fan equipment is placed in a narrow ventilator, the circulation of air may also be influenced and the size of impeller hubs is limited, and the narrow space also limits the application of an adjusting mechanism in a medium or small fan. For example, CN103727062A discloses “a device for adjusting moving blades of an axial flow fan”, wherein the device is mainly composed of moving blades, transmission groups, impeller hubs, a hydraulic transmission system and a control panel, and the hydraulic system provides power in the blade adjusting process, so that the control panel drives the blades to change the installation angles. Such an adjusting structure increases the manufacturing and maintenance cost of the hydraulic system, is not suitable for being applied to a medium or small fan, and cannot realize synchronous adjustment.
In an existing mechanical adjusting type mechanism, e.g., “a device for adjusting moving blades of an axial flow fan” disclosed in CN204386932U, a motor drives a lead screw to rotate so that a nut produces axial displacement, and drives adjusting arms for blades so as to adjust the angles of the blades. The mechanism for adjusting blades is completely placed in a ventilator, thereby leading to the problems that the maintenance is inconvenient and the performance of the fan is influenced, and also failing to realize synchronous adjustment of two-stage blades.
For another example, CN201865932U discloses “an angle adjustable counter-rotating axial flow energy-saving fan for a mine”, wherein a large bevel gear drives a series of small bevel gears to rotate so as to adjust the angles of blades, the synchronism of a plurality of moving blades would be poor in the adjusting process, and the moving blades are asynchronous during primary and secondary adjustment and need to be adjusted by shutdown, which is unbeneficial to the safety of the mine.
Therefore, it is particularly important to develop a two-stage blade adjusting mechanism for a counter-rotating axial flow fan, which is compact in structure and low in manufacturing cost and realizes synchronous adjustment.